红河Eddy Current Displacement Sensor

Working principle:

The working principle of eddy current sensor system is eddy current effect, which belongs to an inductive measurement principle. The eddy current effect results from the energy of the oscillating circuit. Eddy currents need to be formed in conductive materials. An alternating current is introduced into the inner coil of the sensor probe to create a magnetic field around the probe coil. If you put a conductor in this field, according to Faraday's law of electromagnetic induction, eddy currents will be excited within the conductor. According to Lenz's law, the direction of the eddy current's magnetic field is opposite to the coil's magnetic field, and this will change the impedance value of the coil inside the probe. The change in this impedance value is directly related to the distance between the coil and the object being measured. After the sensor probe is connected to the controller, the controller can obtain the variation of voltage value from the sensor probe and calculate the corresponding distance value based on it. The principle of eddy current measurement can measure all conductive materials. Because the eddy current can penetrate the insulator, even if the surface is covered with the metal material of the insulator, it can also be used as the object of the eddy current sensor. The unique coil winding design can not only realize the compact shape of the sensor, but also meet the requirements of its operation in the high temperature measurement environment.

Scope of Application:

By measuring the relative position of the metal measured body and the probe end, the eddy current displacement sensor induces and processes the corresponding electrical signal output. Sensor can work reliably for a long time, high sensitivity, strong anti-interference ability, non-contact measurement, fast response speed is not affected by oil and water and other media, in large rotating machinery axis displacement, axis vibration, axis speed and other parameters of the long-term real-time monitoring is widely used. And has been extended to satellite launch, material identification, weighing measurement, metal plate thickness measurement, material shape variables and other applications.

Technical parameter：

Connection definition：

Product size：

The ML33 sensor system consists of a probe, preprocessor, cable, and accessories.

1、Eddy current sensor probe

Standard probe installation size:

Usually the probe consists of a coil, a head, a shell, a high-frequency cable and a high-frequency connector.

In the production process, the head body of the probe is generally made of high temperature resistant PPS engineering plastics, and the coil is sealed by "secondary injection molding". The probe can work reliably in harsh environment. Because the diameter of the head coil determines the linear range of the sensor system, we usually use the external diameter of the head body to classify and characterize each type of probe. In general, the linear range of the sensor system is roughly 1/2 ~ 1/4 times of the diameter of the probe head. The sensor probe of ML33 series is shown in the figure (standard type) :

The probe housing is used to connect and secure the probe head and is used as a clamping structure for the probe installation. The shell is usually made of brass nickel-plated process, engraved with standard threads and equipped with lock nuts. In order to adapt to different applications and installation occasions, the probe housing has different forms and different threads and dimensions.

Mounting size of countersunk probe:

Installation size of square probe:

Round probe mounting size:

Eddy current sensor preprocessor

The preprocessor is the signal processing center of the whole sensor system. On the one hand, the preprocessor provides high frequency AC excitation current to the probe coil to make the probe work; On the other hand, the preprocessor induces the gap change between the probe head body and the metal conductor in front of the head body through a special circuit. After processing by the preprocessor, the voltage or current output signal changes with the linear change of the gap.

Outline size of ML33 series preprocessor:

Product naming rules

1、Probe

●  A □□:Probe range code selection

▼   Probe code classification 

●  B□□ :No thread length option

  The threaded part of the probe is to facilitate installation, reduce invalid thread length, and make screwing bolts faster

▼Metric threaded probe

●  C□□ :Shell length option

  The length of the probe shell depends on the usage of the field. In order to ensure the measurement accuracy and avoid
the measurement interference from the vibration band of the probe rod, it is recommended not to use the length of the shell
over 300mm long; when necessary, an installation attachment to enhance the strength of the probe rod should be added

▼Metric shell length

● D□□ : Probe shape and structure selection

  This does not represent the standard probe structure; C represents the sink structure; F represents the square probe structure and Y represents the circular probe structure.